The present disclosure relates to process control systems. In particular, the present disclosure relates to wafer rings and flanges in industrial processes.
In processing plants, fluids are conveyed through piping to various processing elements. The piping includes individual pipe sections that are connected together by fittings. Elements, such as sensors and valves, can be introduced into the piping by placing the elements between the fittings of two pipe sections.
In a common configuration, a wafer ring is placed between two pipe sections. The wafer ring includes an outer ring that is positioned annularly about at least one fluid flow passage. One or more holes pass through the outer ring in a radial direction. Sensors may be introduced through the radial holes to interact with the fluid and/or piping may be introduced into the radial holes to direct fluid to a sensor mounted outside of the piping. Further, orifice plates, averaging pitot tubes, other flow obstructions or other components that interact with the process fluid may be positioned within the fluid flow passage of the wafer ring.
Some wafer rings are installed between process pipes by sandwiching the wafer ring between two flange fittings that are then connected together by nuts and studs. Flange fittings generally include a collar that is welded to the end of a pipe, a bore that is aligned with the inner bore of the pipe, an annular sealing section that extends around the bore and a flange section that extends around the annular sealing section. The flange section includes a planar face that has several through holes that accept studs for connecting the fitting to another fitting. The annular sealing section has a sealing face designed to mate with and seal against one or more other elements at the fitting junction.
There are a number of different types of sealing faces including flat, raised, ring-type joint (RTJ), tongue-and-groove, and male-and-female.
A flat sealing face is co-planar with the face of the flange section resulting in a large mating area when the flange fitting is sealed against another flange fitting. A raised sealing face is raised relative to the face of the flange section resulting in a smaller sealing surface but a greater sealing pressure. An RTJ sealing face is a raised face that includes an annular channel that is designed to accept a metallic sealing ring. The metallic sealing ring is compressed as the flange fittings are bolted together causing the ring to come into intimate contact with the surface of the annular channel and thereby form a metallic seal with the channel. A tongue-and-groove sealing face includes one of either a tongue or a grove and is designed to be mated with an opposing sealing surface that contains the other of a tongue or groove. A male-and-female sealing surface includes one of either an inner annular ring or an outer annular ring and is designed to be mated with an opposing sealing surface that contains the other of an inner annular ring or an outer annular ring.